Both wired and wireless communication systems electronic communication systems have come into widespread use, and some systems use a combination of both wired and wireless elements. For example, a communication system may be composed of many mobile wireless transceivers and a set of stationary transceivers which serve to link a wireless transceiver with other wireless transceivers, telephone lines, or some other communication system. An input signal (e.g., a human voice) is received by a mobile transceiver and results in a transmitted signal (e.g., a digital or FM radio signal). The transmitted signal is then received by the stationary transceiver which relays the signal to a receiving mobile transceiver. The mobile transceiver receives the signal (e.g., a digital or FM radio signal) and produces an output signal (e.g., the human voice as presented by a cellular phone speaker).
When a communication system such as the above example is designed, the designer must make decisions regarding where to place the stationary transceivers. Each stationary transceiver typically provides acceptable service over only a limited geographical area due to many variables such as distance, terrain, climate, and interference. When designing other communication systems, other parameters may be involved. Due to the mathematical complexity in determining how these variables affect system performance, communication system developers typically use a computer system running communication system design software to design the communication system.
A useful feature of communication system design software is the ability to predict the performance of the system at a given location. For example, a software tool may be used to design a cellular phone network composed of several transceiver towers. Given a physical location, the software can predict the field strength or power level of a signal from a transceiver tower or choose the strongest signal available from several transceiver towers. In this way, the software provides an indication of the performance of the system as perceived by a communication system user at a particular geographical location. The designer can then use the software to reposition the towers during the design phase in an attempt to find an optimal tower arrangement. As a result, the system designer can design a system providing a desired level of system performance over a greater geographical area while using fewer towers. In addition, the designer avoids the cost of having to actually construct the communication system in order to predict its performance. In wired systems, a location may not be a geographical location, but rather a logical location within elements of the communication system, such as at a particular amplifier or module.
Given a location, the design software may present the predicted attribute of a signal as a numerical value, (e.g., 7.453 dBuV/m). A numerical value, however, is of limited usefulness because prior knowledge and experience are required to determine if the numerical value is within an acceptable range. Further, the numerical value does not provide a readily understandable indication of how the system performance will be perceived by the communication system user.
Some communication system design software addresses these problems by drawing a system map of the communication system. On the map, various colors are used to denote the values of a particular signal attribute at locations on the map. For example, if the attribute at a particular location has a value between 50.0 and 60.0, the software might use the color green when drawing the location on the map. Values between 40.0 and 50.0 might be drawn with blue. In this way, the designer can determine at a glance the approximate values of the signal attribute at a particular location on the map. However, the use of colors still requires prior knowledge and experience to determine if the color is within an acceptable range. Further, the color still does not provide a readily understandable indication of how the system performance will be perceived by the communication system user.
Each of these problems with communication system design software are compounded by the variety of signal types that may be transmitted over a communication system. For instance, voice, data, image, and video may each require a different level of performance. Thus, the numerical value or color generated by the design software may be acceptable for one signal type but not for another.
The invention avoids these problems by providing a simulated output signal. In one embodiment, an attribute of a signal at a particular location is calculated. A model signal is modified according to the calculated attribute to produce a simulated received signal. Interference is calculated and added to the simulated received signal, and modifications are made based on receiver characteristics to produce a simulated output signal. The simulated output signal can then be presented to the designer for evaluation.
In this way, the designer need not know the meaning of particular numerical values but can instead listen to and/or watch an output signal that serves as a simulation of what a communication system user would actually hear or see. For design systems that use color maps, the invention provides an additional way in which to judge system performance and a way to associate the colors with a simulated signal. Since the predicted attribute is presented in the way it would actually be perceived, it is more easily evaluated and understood without prior experience or training.
Additional features and advantages of the invention will be made apparent from the following detailed description of illustrated embodiments which proceeds with reference to the accompanying drawings.